Why it works: Onion and mustard match in chemistry and in kitchens. They rank in the top 6% of all ingredient pairs, and cooks put them together in 9,259 recipes. Both carry 2-isopropyl-3-methoxypyrazine, which smells earthy, pea. The science ↓
To Pickle Onions
Ingredients
Directions
Prepare the onions
Peel the onions until they are white.
Scald the onions in a mixture of salt and water.
Remove the onions with a skimmer.
Pickle and bottle
Boil the vinegar until hot enough to cover the onions.
Strew whole black pepper and white mustard seed over the onions.
Pour the hot vinegar over the onions to cover them.
Once cold, place the onions in wide-mouthed bottles and cork them tightly.
Optionally, add sweet oil to the bottles before sealing.
Transcribed from a scanned cookbook and modernised for today's kitchens. Where the book gave no heat or time, or said "a moderate oven", the temperatures and times here may be modern equivalents rather than the book's own figures.
Explore the science
The flavor team
The pairs that carry this dish. Each one is judged two ways: how much their aromas overlap, and how often cooks already put them together.
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Onion + mustardtop 6% of all pairsSmell alikestrongCooked together9,259 recipes
Shared aroma: 2-isopropyl-3-methoxypyrazine (earthy, pea).
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Vinegar + mustardtop 7% of all pairsSmell alikemoderateCooked together14,067 recipes
Shared aroma: isobutyraldehyde (malty, green).
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Pepper + mustardtop 9% of all pairsSmell alikemoderateCooked together15,430 recipes
Shared aroma: 2-isopropyl-3-methoxypyrazine (earthy, pea).
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Onion + peppertop 11% of all pairsSmell alikemoderateCooked together68,474 recipes
Shared aroma: 2-isopropyl-3-methoxypyrazine (earthy, pea).
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Onion + vinegartop 14% of all pairsSmell alikemoderateCooked together18,226 recipes
Shared aroma: acetic acid (sour, vinegar).
Ranks compare each pair with 20,000 random ingredient pairs on CompKitchen. How we score pairs
What each ingredient does
- Small white onions
- Provide the main vegetable that softens and turns mild and tender in the brine and vinegar.
- White vinegar
- Acidity preserves the onions and gives them their sharp, tangy flavour.
- Coarse sea salt
- Salt draws moisture from the onions during scalding and seasons them throughout.
- Whole black pepper
- Adds a warm, pungent aroma that infuses into the pickling liquid.
- White mustard seed
- Contributes a sharp, pungent flavour and aroma to the pickling liquid.
The step that matters
Scalding the onions in the salt and water. Scalding partly softens the onions and draws out moisture so they take up the vinegar well; scalding too long can make them mushy, and too little leaves them firm and raw-tasting.
Swap the onion
How well each one fits the dish's main ingredients (vinegar, pepper, mustard):
- Horseradishfits better
- Radishfits better
- Lettucefits better
- Onionthe original
Fit is the average pairing score against vinegar, pepper, mustard. Candidates are from the same food group and used in at least 100 recipes.
“What each ingredient does” and “The step that matters” were written by Claude from this recipe’s own method and reviewed in samples by CompKitchen.
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